Question

If 80percent of an element has an atomic mass 42u and 20 percent has an atomic mass 43u. What is the average atomic mass of the mixture?

Answer 1

9'9964
$1465 + 6163 \\ 1314$

Answer 2

42.2 as if u take the average of 

42,42,42,42,42,42,42,42,43,43